1. Technical Field
The present invention relates generally to the control of internal combustion engines and more particularly to a control device and a method for controlling the enrichment of a fuel/air ratio supplied to an internal combustion engine to maintain the temperature of a catalyst in a catalytic converter below a predetermined temperature limit.
2. Discussion
Catalytic converters are used to reduce major air pollutants, such as hydrocarbons, carbon monoxide and oxides of nitrogen, contained in the exhaust gas from an internal combustion engine of a motor vehicle. Each converter contains catalysts that produce an exothermic chemical reaction that transforms noxious pollutants into carbon dioxide and water vapor. The catalytic converter is integrated downstream from the vehicle's engine into the vehicle's exhaust system.
The effectiveness of reducing pollutants by a catalytic converter is highly dependent on the temperature and total gas throughput which in turn depends on the operational states and conditions of the internal combustion engine. Over time, catalyst efficiency degrades and thus decreases the capacity of the converter to convert noxious pollutants. Increasingly stringent federal and state motor vehicle emission standards include regulations on the longevity of emission controlling devices such as catalytic converters.
One factor which causes the performance of the catalytic converter to severely deteriorate over time due is the operation of the catalytic converter at high temperatures for prolonged periods of time. Accordingly, it would be desirable to provide a controller and a method for controlling the operation of the vehicle to maintain the temperature of the catalyst in the catalytic converter below a predetermined temperature limit so as to prolong the effective life of the catalytic converter.